Generally a refrigerator is equipped with an evaporator for cooling air to be circulated therein. After a prolonged use, frost is bound to be formed on the evaporator.
If too much frost gets formed on the evaporator, the cooling performance thereof gets deteriorated and the circulation of the cooled air also gets hindered within the refrigerator by the frost blocking the air passages.
To defrost the frost from the evaporator, the refrigerator is conventionally provided with a defrosting mode. Whether to operate or not in the defrosting mode is determined by a power dissipated for driving a compressor and a variation of the temperature during the driving of the compressor.
However, in the conventional refrigerator, too much frost is usually formed on the evaporator before the refrigerator begins automatically to operate in the defrosting mode, first resulting in blocking of the cooled air passages, resulting in the performance of the refrigerator being deteriorated.